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Scientific Free-Throw Distraction

Every basketball fan knows that the seats behind a backboard don't afford a great view of the court, but they do provide an opportunity to affect a game's outcome. By waving ThunderStix -- those long, skinny balloons that make noise when smacked together -- or other implements of distraction, fans sitting behind the basket can unnerve an opposing team's foul shooters and make them miss. But not, a new theory holds, unless the fans gesticulate in a particular way.

According to Daniel Engber, a basketball fan with a master's degree in neuroscience, the standard "free-throw defenses" are too haphazard to be effective. Fans tend to wave their ThunderStix willy-nilly, creating a unified field of randomly moving objects. Because of the way the human brain perceives motion, free-throw shooters can easily ignore this sort of visual commotion. "Fans might think they're doing something by crazily waving their ThunderStix," Engber says, "but to the players it's all just a sea of visual white noise." Which is why, Engber surmises, N.B.A. teams' free-throw percentages at home and on the road are nearly identical.

The key to a successful free-throw defense, Engber argues, is to make a player perceive a "field of background motion" that tricks his brain into thinking that he himself is moving, thereby throwing off his shooting. In other words, fans should wave their ThunderStix in tandem.

Last season, Engber proposed this tactic to the Dallas Mavericks' owner, Mark Cuban, who took him up on the idea. For three games, Cuban had members of the Mavs' Hoop Troop instruct fans to wave their ThunderStix from side to side in unison. And as Engber subsequently reported in the online magazine Slate, the initial results were encouraging. In the first game, the Mavericks' opponent, the Boston Celtics, shot 60 percent from the line, about 20 percent below their season average. In the second game, the Milwaukee Bucks shot a meager 63 percent. But in the third game, the Los Angeles Lakers shot 78 percent -- about the league average. Which apparently was enough to persuade Cuban to abandon the strategy.

Engber, however, remains a believer. "It's a pretty basic idea when you're studying what kind of perturbations of the visual world affect movement," he says, "that something systematic will have more of an effect than something random."